1. Technical Field
The present invention relates generally to a tie rod assemblies and more particularly to an adjustable tie rod assembly for a parallelogram-type steering system and a method for adjusting a tie rod assembly in a parallelogram-type steering system.
2. Discussion
A conventional parallelogram steering linkage system typically comprises a relay rod that is connected to the frame or chassis of an automobile by two pivoting members, such as a pitman arm and an idler, in a parallelogram arrangement so that the relay rod shifts back and forth laterally in response to steering inputs from the steering wheel of the automobile via a steering gear. The pivoting members are connected to the relay rod by ball joints. The opposite end portions of the relay rod are each connected to a steering knuckle by a tie rod assembly. The tie rod assemblies are connected to the rod by ball joints. The steering knuckles turn the front wheels of the automobile to steer the automobile in response to movements of the relay rod and the tie rods that connect the relay rod to the steering knuckles. The steering knuckles are connected to suspension members by ball joints. Some parallelogram steering linkage systems also include a drag link for moving the relay rod.
Wheel toe is the angular position of the front wheel with respect to a vertical longitudinal plane of the vehicle at zero steering input. Ideally, the wheel toe is zero so that the vehicle tracks in a straight line when the steering input is zero. The wheel toe for each front wheel is adjusted by adjusting the length of the associated tie rod assembly.
One known type of adjustable tie rod assembly has low-friction ball joints at each end and a dual jam nut arrangement for adjustment. This dual jam nut arrangement is shown in FIG. 1 to include a tie rod having oppositely threaded ends. Each threaded end is screwed into an internally threaded portion of a ball joint housing. The tie rod also carries a jam nut at each end that is tightened against the adjacent housing to maintain the depth of the threaded end in the housing. The length of the tie rod assembly is adjusted while connected in the steering linkage system by loosening the two jam nuts and turning the tie rod with respect to the two ball joint housings at the respective ends of the tie rod. The two jam nuts are then tightened down after the adjustment is made to maintain the adjustment.
A disadvantage of the dual jam nut type adjustable tie rod assembly is that two jam nuts must be loosened and then retightened to adjust the length of the assembly. The loosening of the second jam nut frequently causes the tie rod to spin, rendering it more difficult to obtain accurate and precise adjustment of the tie rod assembly. Consequently, the process of adjusting tie rods constructed in this manner can sometimes be an iterative process, especially where the technician has limited experience. Furthermore, automated tooling for adjusting the wheel toe of parallelogram-type steering systems having tie rods with dual jam nuts is not available, necessitating manual adjustment of such systems.
It is one object of the present invention to provide a parallelogram-type steering system having an easily adjusted tie rod assembly.
It is a further object of the present invention to provide a tie rod assembly for a parallelogram-type steering system having a single threaded member to secure the tie rod assembly at a desired position.
It is another object of the present invention to provide a tie rod assembly for a parallelogram-type steering system having a knuckle assembly with a housing that positions an annular connector in a skewed relation to a stem member for connection to a relay rod.
In one form, the present invention provides an adjustable tie rod assembly having a rod member and a knuckle assembly. The knuckle assembly includes a housing and an annular connector. The housing has a stem member and a bore with a longitudinal axis that is skewed to a longitudinal axis of the stem member. The annular connector is disposed in the bore in the housing. The annular connector pivotably couples the first end of the rod member to the housing. The first stem member has an engagement portion that is adapted to be secured to a relay rod.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.